Delayed automatic restart circuit



July 9, 1957 B. EDDY DELAYED AUTOMATIC RESTART CIRCUIT Filed NOV. 1'7, 1954 wan kwm mwm 3m Q New 53 t mwm vwm 5 8 t wR 9m wwn mwm TN SM :n awn 9 {km Qmfl 6w QM H H Qm lNVE/VTOR Lee B. Eddy 4 J W A TTORNE rs.-

2,798,968- DELAYED AUroMAric nnsra'nr cnr curr Lee B. Eddy, Evanston, Ill., assignor to Universal Oil Products Company, D es ltlaincs, Ill, a corporation of Delaware ApplicationNovcmber 17, 1954, Seritii No. 459,368 1 Ciaim. (Cl. 307-35 This invention relates to a delayed automatic restart circuit for electrically operated equipment, particularly for electrically operated equipment that requires large energy or current input durin'g' starting.

In many applications, usually industrial, when the electric power supply is interrupted temporarily and then restored aftera short interval it is desirable, and in many cases essential, that the equipment operatedby the power does not immediately return to operation when the power is restored. These applications are generally when the electrically operated device in questionis one part in a continuity or series of parts Where prior and subsequent parts in that series would be damaged or destroyed unless the part in question remains off or is started in its proper sequence when power is restored. As an example of one of these applications, a pump providing fuel to a burner or a multitude of burners when stopped due to a power failure of even short duration must not start automatically since the restarting of the pump would cause raw unignited fuel to be pumped through the burners and into the furnace thereby creating an extremely dangerous explosion hazard. It is desired in an application such as this that when the pump is momentarily interrupted it remains off until deliberately started by an operator or until an electric igniter is in opertion at which time the fuel may be pumped to the jets and may be properly ignited so that normal operation resumes. In another example certain petroleum processes, such as catalytic reformingv processes, require a high pressure circulating stream of hydrogen to be present during the reforming reactions for many reasons including to prevent deactivation of the catalyst. In the event of a power failure to a reforming process it is desirable that the charge pumps charging liquid petroleum to the process do not start until sufiicient hydrogen circulation has been effected and until suificient heat in the heating means of the process has been established so that the process may resume with a vaporized feed to the reaction section and sufiicient hydrogen therein to prevent deactivation of the catalyst. These are but two examples of a multitude of operations wherein it is desired to not resume operation after a temporary interruption of power and the fact that many more operation exist is evidenced by the widespread use of starter circuits which require a start" button to be pushed in order to restart a machine temporarily stopped by a power interruption.

Although the above described starter button circuit solves the problem of preventing restarting, there is a very annoying, undesirable, and costly intermediate con dition represented by an interruption of the power for an extremely short period, say less than one or two seconds or in some cases even up to seconds or more, in which equipment may resume operation upon the re turn of power without damaging anything. When such a short period of interruption is experienced with the above described starter button circuit, it is necessary to restart all equipment by manually pushing the start ice buttons since evenextremely brief interruptions will cause the circuit to'be' open. This is veryannoying especially when the interruptionisso brief that; for example, the flywheel of a compressorhas maintained it in operation even though the current was off for the period of a few" seconds. To overcome this difliculty a time delay means has been inserted in the circuit which by-passes the magnetic switch for a brief period after the interruption of power so that; inthe' event of a resumption of power within an allowable period, the time delay mechanism will provide a path' of current flow so that the equipment will resume operation even though the start button has not been pushed. The time delay mechanism employed may be of any suitable electrical type which may be based on thermal expansion, fluid passing through anorifice, discharge of a capacitor, decay of a magnetic field, etc.

In any of the above described applications wherein the equipment will start immediately upon resumption of power, particularly after a delay where motor-driven equipment stop's completely or is considerably slowed down, upon resumption of power there is a tremendous drain on" the power source since all of the loads are accelera'ted at the same time. It is well known that the current consumption dur'rng starting and accelerating Ora motor load is' much greater than during normal operatiori'. When a great many electrical loads are all started or accelerated simultaneously, as in the case of returning power after an interruption, the drain is so great upon the available power source that frequently the equipment is unable to accelerate the load or fuses burn out or other difiicu'lties associated with overloading are encountered. The present invention deals with this problem and; it is an object of this invention to provide a circuit for the automatic stagewise starting of equipment following a power interruption.

It is an embodiment of this invention to provide a control circuit for restarting a plurality of electrically operated devices following a power interruption, comprising iii combination electrically actuated time delay means connecting to circuit closing means for energizing some of said electrically operated devices whereby upon the expiration of a predetermined delay period said time delay means acts upon said circu'it closing means to close said circuits.

In a more specific embodiment this invention relates to a control circuit for restarting at least one electrically operated device after a predetermined delay and following a power interruption of limited and predetermined duration comprising in combination four parallel paths for electric current flow across a potential diiference, the first 'of said paths comprising a self-releasing switch which, when closed, provides a closed circuit across said potential difference through said self-releasing switch and mutually parallel paths which pass respectively through a magnetic field producing means and a first time delay means which maintains an electrical contact closed for a certain time following 'de-energization, the second of said parallel paths comprising a switch, cl'osable by said magnetic field and whenfclosed providing a closed circuit across said potential difference through said magnetically closableswitch and mutually. through said magnetic field producing means and said first time delay means, the third of said parallel paths comprising a switch closable by a second time delay means which when closed-provides a closed circuit across said potential difference through the latter switch and mutually through said magnetic field producing means and said first time delay means, said fourth parallel circuit comprising a switch openable by said magnetic field, which when closed provides a circuit across said potential difference through said magnetically openable switch and then through two mutually parallel paths, one

path through a switch closed by said first time delay means and the other path through a switch closed by a second magnetic field producing means with conducting means connecting the latter mutually parallel paths and connecting to second magnetic field producing means and to the aforesaid second time delay means which closes an electrical contact at a predetermined time following energization.

Referring to the drawing, there is here illustrated a modification of this invention wherein a temporary interruption of power will not prevent the equipment from immediately restarting unless its duration is sufliciently long to be objectionable. Time delay means are in the circuit so that a tolerable interruption of power will not cause the circuit to be opened and at the same time the resumption of power will not start all of the equipment at once but in at least two stages with a suitable delay between.

A voltage imposed between lines 301 and 302 causes current to pass through the control circuit disposed therebetween. It may be seen that the start button 307 prevents current from flowing through lines 306 and 307 by causing the circuit to be open. Similarly, switch 316, which is held closed by magnet 310, is open since no current is flowing through magnet 310. Similarly, switch 317, which is actuated only after time delay means 312 has been energized for a preset time, is held open. Switch 319, actuated by said magnet 310, is open when the magnet 310 is energized and conversely switch 319 is closed when magnet 310 is de-energized so that the circuit through line 320 is operative when magnet 310 is deenergized. Switch 321 is actuated by time delay 312 and is held closed when time delay 312 is closed and for a preset time following de-energization of time delay 312. Switch 322 is actuated and held closed when magnet 324 is energized. The stop button is a maintained-contact device in the open-circuit position, and is automatically changed to the closed-circuit position when the start button is pressed.

The function of the various parts and their interrelation now being explained, the method of controlling the circuit will be described in detail. The mechanism is placed in operation by pressing start button 307 which Works against spring 308 and closes the contacts to cause current to flow through line 303, stop button 304, lines 305 and 306, to line 309 from where it passes through magnet 310 and completes the circuit through line 313 to line 302. The magnet 310 when energized, closes switch 316 so that when the start button is released and spring 308 breaks the contact between line 306 and 309, the current is established through the path from line 305, through line 315, through switch 316, through line 318, and then through line 309. Of course when the current is flowing through line 309 magnet 310 is energized maintaining switch 316 closed so that current flows through the circuit to line 302-even though the released start button breaks the circuit between lines 306 and 309. When'the current flows through switch 316, a current flow is also established through time delay means 312 by way of lines 311 and 314. Time delay means 312 for this example may be a thermal device such as a bi-mctal strip anda heatingcoil combination which, when the current is interrupted, will hold a contact closed for the time required for the bimetal strip to cool sufiiciently to cause the contact points to separate. As hereinbefore stated when the contact points in time delay means 312 separate they break the flow of current which maintains switch 321 closed, sothat in normal operation switch 321 is closed. As hereinbefore stated, switch 319 which is held open by the energized magnet 310 prevents theflow of current through line 315 to switch 321 and .322, etc. Thecurrent at this point of the explanation is flowing from line 301 to line 302 and the electrical device is properly functioning.

Assuming a momentary interruption of the current, magnet'310is de-energized so that switch 316 opens thereby preventing the flow through the circuit. However, as switch 316 opens switch 319 closes so that in the event of a resumption of power, current may flow through line 315, through switch 319 and through the parts associated therewith. If the current is interrupted too long, time delay means 312 will open and switch 321 will likewise be opened thereby causing the circuit to not start in the event of a restoration of power unless start button 307 is again pushed. If, however, a power interruption has not been sufficiently long to cause time delay means 312 to open, upon the resumption of power the current will pass through switch 319, through switch 321 and through magnet 324 and line 326. As a result of energizing magnet 324, switch 322 closes which causes current to flow through line 320 and through time delay means 325 and line 327. The flow of current through switch 322 also energizes magnet 324 so that in the event time delay element 312 now opens, the circuit will remain closed and will function properly. The passage of current through time delay element 325 causes the time delay means such as the heating element in the hereinbefore described time delay means to start the timing cycle which upon its completion causes the contact in time delay means 325 to close switch 317 which in turn by-passes both the start button and switch 316 to cause current to flow through magnet 310 and into line 302. With the establishment of current flowing through magnet 310, of course, magnetic switch 316 closes so that the normal path of current flow is resumed and at the same time switch 319 opens so that the current flow through the time delay circuit is stopped since it is no longer necessary.

The embodiment of this invention shown in Figure 4 is perhaps the most useful since it combines a circuit forrestarting in the event of a brief interruption of power but not restarting in the event of a long interruption of power with a suitable time delay to start the various pieces of electrical equipment in a stagewise manner rather than all at once. Pressing stop button 304 breaks the circuit between lines 303 and 305 thereby causing the equipment to stop. Mechanical linkage 328 provides for the stop" button to close the circuit when start button 307 is pushed.

I claim as my invention:

I A control circuit for restarting at least one electrically operated device after a predetermined delay and following a power interruption of limited and predetermined duration comprising in combination four parallel paths for electric current flow across a potential difference, the first of said paths having a self-releasing switch which, when closed, provides a closed circuit across said potential difference through said self-releasing switch and mutually parallel paths which pass respectively through a magnetic field producing means and a first time delay means which maintains an electrical contact closed for a certain time following de-energization, the second of said parallel paths having a switch closable bysaid magnetic field and when closed providing a closed circuit across said potential difference through said magnetically closable switch and mutually through said magnetic field producing means and said first time delay means, the third of said parallel paths having a switch closable by a second time delay means which when closed provides a closed circuit across said potential difference through the latter switch and mutually through said magnetic field producing means and said first time delay means, said fourth parallel circuit having a switch openable by said magnetic field, which when closed provides a circuit across said potential difference through said magnetically openable switch and then through two mutually parallel paths, one path through a switch closed by said first time delay means and the other path through a switch closed by a second magnetic field producing means with conducting means connecting the latter mutually parallel paths and connecting to second magnetic field producing means and to the aforesaid second time delay means which closes an electrical contact at a predetermined time following energization.

References Cited in the file of this patent- UNITED STATES PATENTS Atkinson et al Mar. 25, 1952 Hester July 29, 1952 Holmes et a1. Jan. 25, 1955 

